Neel J P S, Fontenot J P, Clapham W M, Duckett S K, Felton E E D, Scaglia G, Bryan W B
USDA-ARS Appalachian Farming Systems Research Center, Beaver, WV 25813-9423, USA.
J Anim Sci. 2007 Aug;85(8):2012-8. doi: 10.2527/jas.2006-735. Epub 2007 Apr 27.
Angus-crossbred steers (n = 216) were used in a 3-yr study to assess the effects of winter stocker growth rate and finishing system on finishing performance and carcass characteristics. During winter months (December to April) steers were randomly allotted to 3 stocker growth rates: low (0.23 kg x d(-1)), medium (0.45 kg x d(-1)), or high (0.68 kg x d(-1)). Upon completion of the winter phase, steers were randomly allotted within each stocker treatment to a corn silage-concentrate or pasture finishing system. All steers regardless of finishing treatment were finished to an equal-time endpoint to eliminate confounding of treatments with animal age or seasonal factors. Upon completion of the finishing period, steers were slaughtered in 2 groups (one-half of pasture and one-half of feedlot cattle each time) and carcass data were collected. Winter data were analyzed as a completely randomized design, with winter treatment, pen replicate, year, and the winter x year interaction in the model. Finishing performance and carcass data were analyzed in a split-plot design with finishing system in the whole plot, and winter growth rate and winter x finish in the split-plot. Winter treatment mean within finishing replication was the experimental unit, and year was considered a random effect. Winter stocker phase treatments resulted in differences (P < 0.001) in final BW, ADG, and ultrasound LM area between all treatments for that phase. Pasture-finished cattle had lower (P < 0.001) final BW, ADG, HCW, LM area, fat thickness, KPH, dressing percent, USDA yield grade, and USDA quality grade. Winter stocker treatment influenced (P < 0.05) final BW and HCW, with low and medium being less than high. Steers with low stocker gain had greater (P < 0.05) finishing ADG. Dressing percent was greater (P < 0.001) for high than low, and USDA quality grade was greater (P < 0.05) for high than low and medium. Carcass LM area, fat thickness, KPH, and USDA yield grade were not influenced (P > 0.05) by winter rate of gain. Cattle on low during winter exhibited compensatory gain during finishing but were unable to catch the high group regarding BW or HCW. The USDA quality grade was greater for high than low or medium. Animal performance during the winter stocker period clearly impacts finishing performance, carcass quality and beef production in both pasture- and feedlot-finishing systems, when cattle were finished to an equal-time endpoint.
安格斯杂交阉牛（n = 216）被用于一项为期3年的研究，以评估冬季育肥牛生长速度和育肥系统对育肥性能和胴体特性的影响。在冬季月份（12月至4月），阉牛被随机分配到3种育肥牛生长速度组：低（0.23 kg×d⁻¹）、中（0.45 kg×d⁻¹）或高（0.68 kg×d⁻¹）。冬季阶段结束后，在每个育肥牛处理组内，阉牛被随机分配到玉米青贮 - 精料或放牧育肥系统。所有阉牛无论育肥处理如何，均育肥至相同的时间终点，以消除处理与动物年龄或季节因素的混淆。育肥期结束后，阉牛分两组屠宰（每次每组各有一半放牧牛和一半饲养场牛），并收集胴体数据。冬季数据采用完全随机设计进行分析，模型中包含冬季处理、栏舍重复、年份以及冬季×年份交互项。育肥性能和胴体数据采用裂区设计进行分析，整个区组为育肥系统，裂区为冬季生长速度和冬季×育肥处理。育肥重复内的冬季处理平均值为实验单位，年份被视为随机效应。冬季育肥牛阶段处理导致该阶段所有处理组在最终体重、平均日增重（ADG）和超声测定的腰大肌面积上存在差异（P < 0.001）。放牧育肥牛的最终体重、ADG、热胴体重（HCW）、腰大肌面积、脂肪厚度、肾周脂肪比例（KPH）、屠宰率、美国农业部产量等级和美国农业部质量等级较低（P < 0.001）。冬季育肥牛处理影响（P < 0.05）最终体重和HCW，低生长速度和中生长速度组低于高生长速度组。育肥牛生长速度低的阉牛育肥期的平均日增重更高（P < 0.05）。高生长速度组的屠宰率高于低生长速度组（P < 0.001），美国农业部质量等级高生长速度组高于低生长速度组和中生长速度组（P < 0.05）。胴体腰大肌面积、脂肪厚度、KPH和美国农业部产量等级不受冬季生长速度的影响（P > 0.05）。冬季生长速度低的牛在育肥期表现出补偿性生长，但在体重或HCW方面无法赶上高生长速度组。高生长速度组的美国农业部质量等级高于低生长速度组或中生长速度组。当牛育肥至相同的时间终点时，冬季育肥牛阶段的动物性能明显影响放牧和饲养场育肥系统中的育肥性能、胴体质量和牛肉产量。
